1. Field of the Invention
The invention relates to a bidirectional optical amplification system and in particular to a system making it possible, via one and the same optical guide, to transmit optical waves in both directions and to amplify them.
This system applies in particular to transmission on single-mode optical fibres using amplifiers having doped fibre. It allows an intrinsically monodirectional optical amplifier to be made into a bidirectional amplifier. Any existing monodirectional optical transmission can thus be transformed simply, rapidly and cheaply into a multichannel bidirectional transmission.
The device employs existing technologies; it is monobloc and easily insertable, by simple disconnection and reconnection of the optical amplifiers, into an optical transmission.
The areas of application are mainly telecommunications and fibre-optic distribution networks.
2. Discussion of the Background
Fibre-optic transmissions are making ever greater use of optical amplifiers having doped fibre in replacement of the repeaters used formerly and of wavelength multiplexing to multiply the number of channels which can be conveyed within one and the same fibre (see French patent No. 2 258 751).
FIGS. 1 and 2 show the optical transmission diagrams currently used in the areas of telecommunications and distribution networks.
Transmissions in the reverse direction are customarily carried out by twinning the transmission lines.
The optical amplifiers having doped fibre which are ordinarily used, such as the one represented in FIG. 3, are monodirectional on account of their design and of the presence of optical isolators; hence, they do not make it possible to carry out bidirectional transmissions based on optical multiplexing.